It is now a required safety measure to provide guard rail bumper guards in pronounced curbs along motor vehicle highways, to prevent these vehicles from falling into ditches. Some of these road guards have desirably been made from spring-back, elastic components that will provide some measure of yield under the vehicle load, while "rebounding" the vehicle on the road thereafter. A number of patents have issued in this particular field, for example U.S. Pat. No. 4,030,706 dated Jun. 21, 1977 in the name of James S. WARD. In this patent, a pair of automobile tires are arranged concentrically one within the other is with their central mouth engaged therethrough by a rail bumper guard, transversely to its longitudinal axis. Such arrangement is of course crude (as seen in FIG. 1 of the Ward patent), and is of overall low impact absorbing capability.
In U.S. Pat. No. 4,186,913 issued Feb. 5, 1980 to A. Bruner et al , the road guard includes a plurality of uprightly disposed, used, pneumatic tires 8, supported by and embedded into a reinforced resilient base. This traffic divider is used both as a resilient bumper as well as a road divider or safety rail. Hence, when the barrier is used as a safety divider alongside a road, a vehicle striking this barrier would be diverted with minimum damage back on the roadway.
A tire is a pneumatic structure, of generally toroidal shape, for encircling the wheels of a road-going vehicle. A tire conventionally includes a radially outward, road surface engaging tread, a pair of opposite, radially inward, wheel rim engaging, annular wires, and a pair of side walls integrally joining the tread (via a pair of opposite annular beads) to the pair of wires. The discrete external covering of synthetic rubber (the tread) is reinforced with a steel belt and fabric ply, laminated against the interior face of the tread. The tire further defines a radially inward, annular mouth, forming the gap separating the two wires, for through passage of the inflatable, cushioning inner tube. The wires and steel belt are embedded into the synthetic rubber of the tire.
Most current passenger car tires have an overall diameter ranging from about 60 to 75 centimeters (cm), such tires constituting the overwhelming bulk of the used tire market. This in turn means that the developed length of any given tire tread would then range approximately from 190 to 235 cm (3.141592.times.60 to 75).
It is understood that a so-called "used" tire is a tire whose tread thickness has been substantially reduced by road-borne frictional forces, up to a point where efficient road surface contact by the tire is compromised in such a way that hazardous road-going conditions appear. That is to say, the remaining tire components usually retain substantially all their original performance features, including the steel belt and the metallic wires.
Such use of used tires as impact absorbers on road guards is all the more desirable, in that current methods of tire recycling are not cost-effective. Indeed, the tire recycling end product, usually rubber powder, cannot be sold at a competitive price, because the cost in manpower and particularly in energy requirements to transform the tire into powder--including separation of the steel wires and steel belt from the rubber material proper--exceeds the market price for such rubber powder. Government subsidies are therefore a prerequisite for such business endeavours.
Currently, the used tire reclaiming process operates in three main steps, each representing about a third of the reclaiming costs to the recycling plant operator:
(a) slashing the tire into shreds; PA1 (b) setting apart the steel from the rubber; PA1 (c) transforming the rubber shreds into a granular compound, by grinding same into a fine powder.